int main()
{
	int n,i,j,k,know,known,yes=0;
	scanf("%d",&n);
	int famous[n],chance[n];
	for(i=0;i<n;i++)famous[i]=0,chance[i]=1;
	for(i=0;;i++)
	{
		scanf("%d%d",&know,&known);
		if(know==0&&known==0)break;
		chance[know]--;
		famous[known]++;
	}
	for(i=0;i<n;i++)
	{
		if(chance[i]==1&&famous[i]==n-1){printf("%d\n",i);yes=1;}
	}
	if(yes==0)printf("NOT FOUND\n");
} 